1. Field of the Invention
The invention relates to a device for determining the moment when the finishing line is passed by competitors in a race in which each competitor is provided with a transmitter, said device comprising at least two receiving antennae at the finishing line and receivers connected to the receiving antennae.
The methods of electronic timing permit a very accurate determination of competition times. In many cases, however, the exact determination of the moment when the finishing line is passed, is critical. When a light barrier extending along the finishing line is used, and several competitors are passing the finishing line in a close order, it is only possible to indicate the exact moment of the passing of the line of the first competitor among several participants passing the line nearly at the same time. If light barriers are mounted vertically relative to the racing course, a mounting bridging the racing course must be erected at the finishing line. In car races, such a bridge is dangerous for the competitors and offers an obstruction of visibility for spectators. Moreover, it is disadvantageous for light barriers that the light transmitters and light receivers may become dirty and that manipulations and interferences by unauthorized persons are to be expected.
2. Description of the Prior Art
There has beek known a system for taking and indicating competition times (German Pat. Appln. Ser. No. 2141001) in which in the ground of the racing course at the finishing line two receiving antennae are mounted which consist of two adjacent conductor loops over which the competitors of a car race will drive consecutively. Each competitor is provided with a transmitter which transmits a selective characteristic. Receivers are connected to the receiving antennae and tuned selectively to the characteristics of the transmitters. When the receiving antennae are passed, the transmitters produce signals which are evaluated and which do not only allow to determine the passing of the finishing line but also to identify the corresponding competitor. The signals produced consecutively in the two antennae, when overtravelled, are added up. The resultant total signal curve contains three sequential voltage peaks. However, it is difficult to evaluate or identify such a signal curve with electronic means for the exact determination of the moment when the finishing line is passed. While the transmitter of each racing car approximately generates approximately the same time voltage curve at the antennae, the amplitudes of curves may considerably vary from each other subject to the different moments when the finishing line is passed. The reason for it may for inst. reside in the different transmitting powers of the individual transmitters or in the different distances of the transmitters from the racing course. If the signal for the passing of the finishing line is only produced after a regular sequence of three voltage peaks has been determined at the receiving antennae, the racing car has already passed the finishing line so that the indicated moment of the passing is not in exact agreement with the real moment of passing.
Moreover, the known antennae system is very sensitive concerning disturbances caused intentionally. E.g. it is possible to set up near the antennae system a transmitter which produces a signal curve comprising three voltage peaks to simulate a passing of the finishing line. The receiving system would be also responsive to such a stationary transmitter for it only analyses the total voltge curve of all three antennae in common, without screening as to whether the voltage maxima occur consecutively at the individual antennae.
It is the object of the invention to provide a device of the type stated at the outset hereof which permits to determine very quickly and exactly the passing of the finishing line and which is insensitive to short-distance and remote interferences in that it is only responsive to transmitters in motion rather than to stationary transmitters.